Self-tightening drill chuck

Abstract

A drill chuck has an axially centered chuck body, an adjustment body rotatable but axially fixed on the chuck body, and jaws radially displaceable on the chuck body. The adjustment body is formed with a screwthread meshing with teeth of the jaws so that relative rotation of the bodies in a tightening direction moves the jaws together and opposite rotation moves them apart. A radially outwardly projecting tab fixed on the chuck body has a pair of angularly oppositely directed end faces and a locking ring axially displaceable on the chuck body between freeing locking positions is formed with an inwardly open pocket receiving the tab and having a pair of angularly confronting end faces engageable with the respective end faces of the tab and spaced angularly apart by a distance substantially greater than the tab width. A tightening spring connected between the locking ring and chuck body urges the locking ring in the tightening direction. Axially interengageable coupling formations on the locking ring and adjustment body rotationally couple the locking ring to the adjustment body in the locking position of the locking ring and permit relative rotation of the locking ring and adjustment body in the freeing position of the locking ring. At least one locking spring braced between the chuck body and the locking ring urges the locking ring into the locking position.

We claim: 
     
       1. A self-tightening drill chuck comprising: a chuck body centered on and rotatable about an axis;   an adjustment body rotatable but axially not displaceable on the chuck body;   a plurality of jaws radially displaceable on one of the bodies and each formed with a row of teeth, the other body being formed with a screwthread meshing with the jaw teeth, whereby rotation of the one body relative to the other body in a tightening direction moves the jaws together and rotation in the opposite direction moves the jaws apart;   a radially outwardly projecting tab fixed on the chuck body having a pair of angularly oppositely directed front and back end faces spaced angularly apart by a predetermined tab width;   a locking ring axially displaceable on the chuck body between a freeing position and a locking position and formed with a radially inwardly open pocket receiving the tab and having a pair of angularly confronting front and back end faces engageable with the respective end faces of the tab and spaced angularly apart by a distance substantially greater than the tab width, whereby the tab can move angularly in the pocket;   a tightening spring connected between the locking ring and chuck body urging the locking ring rotationally on the body in the tightening direction;   axially interengageable coupling formations on the locking ring and adjustment body rotationally coupling the locking ring to the adjustment body in the locking position of the locking ring and permitting relative rotation of the locking ring and adjustment body in the freeing position of the locking ring; and   at least one locking spring braced between the chuck body and the locking ring urging the locking ring into the locking position.   
     
     
       2. The self-tightening drill chuck defined in claim 1 wherein the chuck has three such tabs angular equispaced about the axis and the ring is formed with three such respective pockets also angularly equispaced about the axis. 
     
     
       3. The self-tightening drill chuck defined in claim 1 wherein the chuck body is provided with an annular coupling ring formed with the tab and the chuck body and coupling ring are formed with complementary angularly interengaging formations rotationally coupling the coupling ring and chuck body together. 
     
     
       4. The self-tightening drill chuck defined in claim 3 wherein the chuck body has a rim on which a coupling rim sits. 
     
     
       5. The self-tightening drill chuck defined in claim 3 wherein the formation of the coupling ring is a radially inwardly directed bump and the complementary formation of the chuck body is a radially outwardly directed recess receiving the bump. 
     
     
       6. The self-tightening drill chuck defined in claim 3 wherein the tightening spring is a tension spring having one end hooked on the coupling ring and another end hooked on the locking ring, the tension spring being wrapped around and engaging radially inward on the chuck body. 
     
     
       7. The self-tightening drill chuck defined in claim 6 wherein the coupling ring is formed with an angularly extending and radially inwardly open recess receiving the tension spring and less than 180° long. 
     
     
       8. The self-tightening drill chuck defined in claim 1 wherein the tab is flat and has bent-down edges forming the respective end faces. 
     
     
       9. The self-tightening drill chuck defined in claim 1 wherein the pocket has an axially directed cam surface on which the tab rides and having a ramp and a seat, the ramp and seat being so positioned that as the tab rides up on the ramp the locking ring is cammed into the freeing position and when in the seat the locking ring is held in the freeing position. 
     
     
       10. The self-tightening drill chuck defined in claim 9 wherein the seat is positioned at the back end face of the pocket relative to the tightening direction. 
     
     
       11. The self-tightening drill chuck defined in claim 9 wherein the ramp is angled and the tightening spring is of such a force that the tightening spring alone cannot displace the tab angularly up the ramp to the seat. 
     
     
       12. The self-tightening drill chuck defined in claim 1 wherein the coupling formations are so formed and the tightening spring has a force such that the tightening spring alone cannot make the locking-element formations slip angularly on the adjustment-body formations. 
     
     
       13. The self-tightening drill chuck defined in claim 1 wherein the formations are teeth with angled flanks.